Unified reading rle images

src/ImageSharp/Formats/Tga/TgaDecoderCore.cs

@@ -84,7 +84,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
                     case 24:
                         if (this.fileHeader.ImageType.IsRunLengthEncoded())
                         {
-                            this.ReadRle24(pixels, this.fileHeader.Width, this.fileHeader.Height);
+                            this.ReadRle(this.fileHeader.Width, this.fileHeader.Height, pixels, 3);
                         }
                         else
                         {
@@ -96,7 +96,7 @@ namespace SixLabors.ImageSharp.Formats.Tga
                     case 32:
                         if (this.fileHeader.ImageType.IsRunLengthEncoded())
                         {
-                            this.ReadRle32(pixels, this.fileHeader.Width, this.fileHeader.Height);
+                            this.ReadRle(this.fileHeader.Width, this.fileHeader.Height, pixels, 4);
                         }
                         else
                         {
@@ -197,64 +197,6 @@ namespace SixLabors.ImageSharp.Formats.Tga
             }
         }
 
-        private void ReadRle24<TPixel>(Buffer2D<TPixel> pixels, int width, int height)
-            where TPixel : struct, IPixel<TPixel>
-        {
-            TPixel color = default;
-            using (IMemoryOwner<byte> buffer = this.memoryAllocator.Allocate<byte>(width * height * 3, AllocationOptions.Clean))
-            {
-                Span<byte> bufferSpan = buffer.GetSpan();
-                this.UncompressRle24(width, height, bufferSpan);
-                for (int y = 0; y < height; y++)
-                {
-                    Span<TPixel> pixelRow = pixels.GetRowSpan(this.fileHeader.Height - y - 1);
-                    for (int x = 0; x < width; x++)
-                    {
-                        int idx = (y * width * 3) + (x * 3);
-                        color.FromBgr24(Unsafe.As<byte, Bgr24>(ref bufferSpan[idx]));
-                        pixelRow[x] = color;
-                    }
-                }
-            }
-        }
-
-        private void UncompressRle24(int width, int height, Span<byte> buffer)
-        {
-            int uncompressedPixels = 0;
-            var pixel = new byte[3];
-            int totalPixels = width * height;
-            while (uncompressedPixels < totalPixels)
-            {
-                byte runLengthByte = (byte)this.currentStream.ReadByte();
-
-                // The high bit of a run length packet is set to 1.
-                int highBit = runLengthByte >> 7;
-                if (highBit == 1)
-                {
-                    int runLength = runLengthByte & 127;
-                    this.currentStream.Read(pixel, 0, 3);
-                    int bufferIdx = uncompressedPixels * 3;
-                    for (int i = 0; i < runLength + 1; i++, uncompressedPixels++)
-                    {
-                        pixel.AsSpan().CopyTo(buffer.Slice(bufferIdx));
-                        bufferIdx += 3;
-                    }
-                }
-                else
-                {
-                    // Non-run-length encoded packet.
-                    int runLength = runLengthByte;
-                    int bufferIdx = uncompressedPixels * 3;
-                    for (int i = 0; i < runLength + 1; i++, uncompressedPixels++)
-                    {
-                        this.currentStream.Read(pixel, 0, 3);
-                        pixel.AsSpan().CopyTo(buffer.Slice(bufferIdx));
-                        bufferIdx += 3;
-                    }
-                }
-            }
-        }
-
         private void ReadBgra32<TPixel>(Buffer2D<TPixel> pixels)
             where TPixel : struct, IPixel<TPixel>
         {
@@ -273,31 +215,41 @@ namespace SixLabors.ImageSharp.Formats.Tga
             }
         }
 
-        private void ReadRle32<TPixel>(Buffer2D<TPixel> pixels, int width, int height)
+        private void ReadRle<TPixel>(int width, int height, Buffer2D<TPixel> pixels, int bytesPerPixel)
             where TPixel : struct, IPixel<TPixel>
         {
             TPixel color = default;
-            using (IMemoryOwner<byte> buffer = this.memoryAllocator.Allocate<byte>(width * height * 4, AllocationOptions.Clean))
+            using (IMemoryOwner<byte> buffer = this.memoryAllocator.Allocate<byte>(width * height * bytesPerPixel, AllocationOptions.Clean))
             {
                 Span<byte> bufferSpan = buffer.GetSpan();
-                this.UncompressRle32(width, height, bufferSpan);
+                this.UncompressRle(width, height, bufferSpan, bytesPerPixel);
                 for (int y = 0; y < height; y++)
                 {
                     Span<TPixel> pixelRow = pixels.GetRowSpan(this.fileHeader.Height - y - 1);
+                    int rowStartIdx = y * width * bytesPerPixel;
                     for (int x = 0; x < width; x++)
                     {
-                        int idx = (y * width * 4) + (x * 4);
+                        int idx = rowStartIdx + (x * bytesPerPixel);
-                        color.FromBgra32(Unsafe.As<byte, Bgra32>(ref bufferSpan[idx]));
+                        switch (bytesPerPixel)
+                        {
+                            case 4:
+                                color.FromBgra32(Unsafe.As<byte, Bgra32>(ref bufferSpan[idx]));
+                                break;
+                            case 3:
+                                color.FromBgr24(Unsafe.As<byte, Bgr24>(ref bufferSpan[idx]));
+                                break;
+                        }
+
                         pixelRow[x] = color;
                     }
                 }
             }
         }
 
-        private void UncompressRle32(int width, int height, Span<byte> buffer)
+        private void UncompressRle(int width, int height, Span<byte> buffer, int bytesPerPixel)
         {
             int uncompressedPixels = 0;
-            var pixel = new byte[4];
+            var pixel = new byte[bytesPerPixel];
             int totalPixels = width * height;
             while (uncompressedPixels < totalPixels)
             {
@@ -308,24 +260,24 @@ namespace SixLabors.ImageSharp.Formats.Tga
                 if (highBit == 1)
                 {
                     int runLength = runLengthByte & 127;
-                    this.currentStream.Read(pixel, 0, 4);
+                    this.currentStream.Read(pixel, 0, bytesPerPixel);
-                    int bufferIdx = uncompressedPixels * 4;
+                    int bufferIdx = uncompressedPixels * bytesPerPixel;
                     for (int i = 0; i < runLength + 1; i++, uncompressedPixels++)
                     {
                         pixel.AsSpan().CopyTo(buffer.Slice(bufferIdx));
-                        bufferIdx += 4;
+                        bufferIdx += bytesPerPixel;
                     }
                 }
                 else
                 {
                     // Non-run-length encoded packet.
                     int runLength = runLengthByte;
-                    int bufferIdx = uncompressedPixels * 4;
+                    int bufferIdx = uncompressedPixels * bytesPerPixel;
                     for (int i = 0; i < runLength + 1; i++, uncompressedPixels++)
                     {
-                        this.currentStream.Read(pixel, 0, 4);
+                        this.currentStream.Read(pixel, 0, bytesPerPixel);
                         pixel.AsSpan().CopyTo(buffer.Slice(bufferIdx));
-                        bufferIdx += 4;
+                        bufferIdx += bytesPerPixel;
                     }
                 }
             }